1. Field of the Invention
The disclosed technology relates to a pixel and an organic light emitting diode (OLED) display using the same, and particularly, to a pixel for improving a contrast ratio of a high-resolution organic light emitting diode display and an organic light emitting diode display including the same.
2. Description of the Related Technology
Various flat panel displays that have reduced weight and volume as compared to cathode ray tube technology have been developed. The flat panel display technologies include liquid crystal display (LCD), field emission display (FED), plasma display panel (PDP), organic light emitting diode (OLED) display, and the like.
An organic light emitting diode (OLED) display displays images by using organic light emitting diodes (OLED) that generate light by recombining electrons and holes. An OLED display has a fast response speed, is driven with low power consumption, and has excellent emission efficiency, luminance, and viewing angle, has recently been in the limelight.
A driving method of the organic light emitting diode (OLED) display is generally classified into a passive matrix type and an active matrix type.
The passive matrix type of driving method has alternately arranged anodes and cathodes in the display area in a matrix form, and pixels are formed at intersections of the anodes and the cathodes.
The active matrix type of driving method has a thin film transistor for each pixel and controls each pixel by using the thin film transistor. The active matrix type of driving method has less parasitic capacitance and power consumption compared to the passive matrix type of driving method, but it has a drawback of non-uniform luminance.
Particularly, current density of the thin film transistor for a high resolution structure is increased and material efficiency is increased by developing a material of the organic light emitting diode so a black current for displaying a black image relatively rises. That is, when the black current that is a minimum current for displaying the black image is transmitted, the pixel including the efficiency-improved organic light emitting diode displays an image that is brighter than the black luminance corresponding to the black current. Therefore, the contrast ratio of the entire display image of a panel including the pixel is deteriorated. Accordingly, the pixel or the display device must be studied in order to control a flow of a minimum driving current transmitted to the organic light emitting diode and maintain a high contrast ratio on a display screen.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.